A longitudinal study of the development of nighttime sleep parameters and daytime sleepiness and performance throughout adolescence is proposed. This period of the life cycle is emphasized because large differences in 24-hour sleep/wake functions have been found between college students and pre-adolescent children; pathological sleepiness associated with narcolepsy and Kleine-Levin syndromes characteristically begins in adolescence; and normative data are needed to facilitate early diagnosis and treatment of pathologically sleepy children and adolescents. The study will follow children 10-13 years of age with yearly studies in the Stanford Summer Sleep Camp until they reach 17-20 years. The study population includes (a) normal boys and girls; (b) children who have a parent with narcolepsy; (c) children with learning disorders; and (d) children who are pathologically sleepy. The protocol accomplishes 24-hour monitoring of sleep and daytime functions during a full week in the Sleep Camp. In addition to basal observations, each subject undergoes sleep loss on one night to evaluate individual daytime sleepiness responses. The nighttime measures include standard sleep parameters, respiratory variables, and motility. Daytime measures include mood scales, Wilkinson Addition Test, Williams Word Memory Test, a listening attention task, and the Multiple Sleep Latency Test. The latter appears to be the most sensitive procedure for detecting individual differences in daytime sleepiness and changes caused by sleep loss. Sexual maturation is followed by yearly evaluations on the Tanner Scale. Two years of the longitudinal study have been successfully completed without HEW-NIH funding. The protocols are eminently feasible. Preliminary results suggest that daytime sleepiness increases with sexual maturation. Pre-adolescent children are extremely alert though individual differences are apparent.